Negative pressure air bearing slider with a choke for restricting air flow

ABSTRACT

A negative pressure air-bearing slider comprises a slider body having a surface with a leading edge, a trailing edge and first and second side edges. First and second raised side rails are positioned along cross rail extends between the first and second raised side rails. The raised cross rail has a leading edge and a trailing edge. A negative pressure cavity extends from the raised cross rail toward the trailing edge and between the side rails. A choke is positioned within the raised cross rail, which widens from the leading edge of the raised cross rail toward the trailing edge of the raised cross rail.

This is a continuation of application Ser. No. 07/867,760 filed on Apr.13, 1992, abandoned as of the date of this application, which is adivisional of application Ser. No. 07/528,925 filed May 25, 1990 andissued as U.S. Pat. No. 5,128,822.

BACKGROUND OF THE INVENTION

The invention relates generally to transducer head assemblies formagnetic recording on rotating disk drives, and more particularly toself-loading negative pressure air bearing sliders for use with rotaryactuators.

Magnetic head assemblies that fly relative to a rotating magnetic diskhave been used extensively. Typically these heads comprise a slider uponwhose trailing end a transducer is mounted. Slider designers would liketo have the magnetic transducer fly as close to the disk as possible,and have the flying height be uniform regardless of variable flyingconditions, such as speed variation from inside track to outside, seeks,and skew caused by rotary actuators. Flying height is viewed as one ofthe most critical parameters of non-contact magnetic recording.

As disk drives become increasingly compact, rotary actuators with shortpivot arms are increasingly employed. However, these actuators increasethe difficulty of flying height control because a rotary actuator causesthe geometric orientation between the slider fixed to the pivot arm, andthe disk rotation tangent, to change as the actuator moves the sliderover the disk surface. A measure of this orientation is given by theskew angle 14 as shown in FIG. 1, which is defined as the angle betweenthe slider's longitudinal axis and the direction of disk's tangentialvelocity. (The "wind" caused by disk rotation is approximately parallelto this tangent.) With the strive towards more compact disk drivepackages for applications in smaller more portable equipment, thedesigner is motivated to use a short actuator pivot arm and thus createrather large skew angles.

However, conventional sliders are very sensitive to skew angle. Evenwith moderate skew angles in the 10-15 degree range, a conventionalslider's fly height and roll angle (defined as the difference in flyingheight between the inside and outside rails, see FIG. 1b) are adverselyinfluenced.

Increasing the skew angle at a fixed tangential velocity causes theslider pressure distribution to become distorted. This influences thenet forces and torque acting upon the slider and results in bothdecreased flying height and increased roll. Because a transducer islocated at the trailing edge of a rail (as is conventional) roll affectstransducer performance because of greater flying height variations.

The effect of flying at a skewed angle also extends slider lift offthereby increasing wear and exacerbates the negative effects of rapidseek. Furthermore, conventional sliders are very sensitive to disksurface speeds. With linear actuation (skew angle is a constant 0°),flying height is higher at outer disk radii. While this may bealleviated somewhat with optimized rotary actuator designs, the flyingheight is still dependent upon disk speed.

A conventional "zero load" or negative pressure air bearing ("NPABN")slider can achieve a flying height substantially independent of diskspeeds. However, at skewed conditions, the NPAB exhibits excessive rolland average flying height loss because the downstream rail receiveslittle air from the negative pressure cavity while at the same time theupstream rail is receiving air at ambient pressure.

The art needs a negative pressure air-bearing slider having a nearconstant, but low, flying height when used in conjunction with short armrotary actuators and/or with high seek velocities wherein reading from adisk during seek is continued, for example, to read track addresses.Preferably, the slider will exhibit little or no roll over a widevariation in skew angles. The slider would also preferably have rapidtake-off but still fly low at full speed.

SUMMARY OF THE INVENTION

The present invention comprises a negative pressure air-bearing sliderhaving reduced skew angle effects. In one configuration isolationchannels situated on the inside of the "catamaran" rails of the slider,adjacent the negative pressure cavity, provide air to the downstreamrail when the slider is skewed, which increases the pressure at thisrail and thereby decreases slider roll.

In one variation, the edges of the rails communicating with the channelsare chamfered to provide an air "scoop" when a rail is sliding at skewand is downstream from a channel. The additional air aids inpressurization of the downstream rail.

Additionally, the upstream edges of the rails are similarly chamfered toprovide the same effect when a rail is sliding at skew with its upstreamedge into the "wind". Increasing pressurization at both the upstream anddownstream rail at skew lessens the reduction in overall flying heightcaused by skew.

The loss of flying height at skew may be further lessened by partiallyspoiling the negative pressure in the negative pressure cavity inresponse to skew. In one configuration, angled air channels are providedinto the cavity. Air flow into the cavity increases with skew as thechannels increasingly align with the direction of slider motion or winddirection.

The use of isolation channels causes the NPAB to have greatersensitivity to flying speed because of the reduced interaction of thepositive and negative pressure effects. The increase in flying height athigher disk surface speeds can be lessened either by shortening orwidening the isolation channel separating rail near the trailing edge ofthe flyer. Further improvement can be provided by a centrally positionedisland located at the trailing edge of the negative pressure cavity.This island can then be used to mount a centrally positioned transducer.

The spoiler channels may be preferably combined with a divided negativepressure cavity to more greatly reduce negative pressure effects in thedownstream cavity. This raises the downstream side of the slider andreduces roll.

Fast take-off is provided by increasing lift at the forward edge of theslider and spoiling negative pressure at low speeds. In a preferredembodiment, the forward lift is provided by extending the area of theforward tapered surface. However, without compensation, a large forwardtaper causes the slider to fly too high at speed and further is far tooresponsive to speed variation from inside to outside disk tracks.Compensation is provided by a pressure reduction channel behind theleading taper and in front of the negative pressure cavity cross rail.This "anterior" pressure reduction channel reduces and flattens theresponse curve of overall flying height versus speed but still providesa faster take-off than conventional designs.

A low speed, negative pressure spoiler is provided by either a choke gapor a resistive flow channel in the cross rail. At low speeds, airtraverse the choke or channel in volumes sufficient to spoil thenegative pressure. However, at high speeds the spoiler's capacitylimitations have a significantly reduced effect on negative pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is bottom plan view of a conventional H-shaped NPAB slider andan illustration of the angle defined to be skew angle.

FIG. 1b is an illustration showing, in great exaggeration, roll for aNPAB slider under influence of wind from the direction shown in 1a.

FIG. 1c is a partial side plan view showing a slider riding on an airbearing above a disk surface.

FIGS. 2a-2d are various views of the conventional H-shaped negativepressure air-bearing slider as modified with isolation channelsaccording to the present invention, including in FIG. 2c a deep versionof the isolation channel and wherein the rail edges are stepped; andFIG. 2d having a shallow version of the isolation channel and whereinthe rail edges are chamfered.

FIGS. 3a-3k are bottom plan views of alternative configurations of aNPAB slider having isolation channels of the present invention.

FIGS. 4a-4f are bottom plan views of alternative embodiments of thepresent invention having a take-off assist spoiler and either isolationchannels or a divided negative pressure cavity, (FIG. 4f has both).

FIG. 5a-5g are bottom plan views of alternative embodiments having fasttake-off extended front tapers and anterior pressure reduction channels.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1a is a bottom plan view of a conventional H-shaped NPAB slider 10flying into wind 12 at an angle θ. The source of the wind is therotation of the disk surface below the slider, movement of the sliderrelative to the surface by the disk drive's actuator arm (not shown)during seek, and/or the wind from the sweeping action of the rotatingdisk surface.

The conventional NPAB slider 10 has two "high pressure" rails 20 and 22(each of which has a leading taper 25, 27 respectively for funnellingair under the rails) a cross rail 24, a negative pressure cavity 28, anda leading cavity 26.

With the wind impacting the slider 10 as shown in FIG. 1a, leading (orupstream) rail 22 remains pressurized, but to a lesser extent than whenthe slider 10 is flying directly into the wind with a skew angle of 0°,both because of the shortened rail length relative to the direction ofmotion and because of the diminished effect of the forward tapers whichact as "scoops" to funnel air under the rails. As the negative pressurecavity does not permit air to traverse laterally to the trailing (ordownstream) rail 20, much less air reaches this rail for pressurization.The net result is that the leading rail 22 drops slightly, the trailingrail 20 drops even more and entire slider 10 f lies at a reduced height.

FIG. 1b shows slider roll in great exaggeration. Normally, slider 10will fly about eight microinches off the disk surface 11 with each rail20, 22 about the same distance from the disk surface 11. If the slider'smotion relative to a disk tangent is skewed (θ>0° or θ<0°) , theconventional slider rolls. A two micro inch difference in flying heightbetween the trailing and leading rails 20 and 22 is considered to be alarge roll.

In FIG. 1b, H ROLL is the difference in flying height of the two rails20 and 22, and H MIN is the flying height of the lowest rail (in thiscase rail 20). Significantly, when slider 10 rolls, H MIN also decreasesfrom its value when there is zero roll. If H MIN decreases too much, notonly is transducer performance affected, but the head could "crash",causing catastrophic failure.

FIG. 1c is a partial side plan view of the slider 10 flying close todisk surface 11. As stated above, typical flying heights are eightmicroinches.

The conventional H-shaped slider 10 has a leading cavity 26, which ispreferably made deep, and which may be a cut through the whole sliderbody. This leading cavity 26 reduces the flying pitch of the slider 10and thereby the height to which it would otherwise fly.

Just aft of the leading cavity 26 is a cross rail (or cross bar) 24. Thecross rail 24 is preferably recessed slightly (by about fortymicroinches from the level of the rails 20, 22. This prevents smallparticles of debris from collecting in the leading cavity 26. The recessin the cross rail 24 slightly reduces the negative pressureeffectiveness of the negative pressure cavity 28. However, it alsoallows some air into the negative pressure cavity 28 on take-off toreduce the negative pressure holding the slider 10 to the disk surface11.

The use of the recessed cross rail 24 is optional. It has been includedas an example in several of the embodiments that follow in the Figures.The importance of a recessed cross rail is not a requirement forobtaining the beneficial effects of the other features described.

Typically, the negative pressure cavity 28 will be a recess 350microinches deep from the level of the rails 20 and 22. The conventionalslider body is typically 0.125" wide, 0.160" long and 0.034" high. Theleading tapered edges 25 and 27, taper to a depth of 200 microinchesfrom the level of the rails 20, 22. Each rail 20, 22 is approximately0.026" wide and the cavity 28 is 0.071" wide at the cross rail 24.Unless otherwise mentioned, the dimensions of the sliders of thepreferred embodiments are generally similar to the dimensions of theconventional H-shaped NPAB slider 10 of FIGS. 1a-1c. It should be notedthat the slider dimensions can be scaled up or down to achieve larger orsmaller sliders with similar characteristics.

FIG. 1c also shows a feature which is not found in the prior art: a step29 in cavity depth of cavity 28. This feature will be discussed in moredetail later.

The first embodiment of the present invention is shown in FIGS. 2a-2d.Isolation channels 30 and 32 extending from the forward edge of theslider to the trailing edge are located adjacent to the inside of thepositive pressure rails 20 and 22 and provide a source of near ambientpressure air along their length. When a slider is flying at a skewedangle, the trailing rail 20 draws air from channel 32 to pressurize andlift the slider on the downstream side, thus reducing roll. Locatedbetween channels 30 and 32 and negative pressure cavity 28 areseparating rails 22' and 20', respectively.

FIG. 2b is a detailed cross section showing rail 22, isolation channel30, separating rail 22' and negative pressure cavity 28. The channels 30and 32 are made relatively deep and wide (e.g., 0.004"×0.004") in orderto provide as little pressure drop along their length as possible,.

FIG. 2c shows a similar cross section of rail 22, isolation channel 30,cavity 28 and the isolation channel separating rail 22' separating theisolation channel from the cavity. In the embodiment of FIG. 2c theedges of the rails include steps 21, 23 for easing the transition of airfrom a rail edge to the rail itself. These optional edges are preferablychamfered as shown in the embodiment of FIG. 2d. However, processingchamfered edges is difficult, while steps can be formed fromconventional processes such as ion milling.

The inside step 23 eases the transition of air from the channel 30 tothe rail 22 when the channel is "upstream" from the rail and aids inpressurization along the entire length of the rail. Step 21 similarlyaids in pressurization of the rail 22 along its entire length when it isflying upstream to the rail (into the wind).

In FIG. 2c, rail 22 is 0.02" wide, channel 30 is 0.004" wide, andisolation channel separating rail 22' is 0.002" wide. The key feature ofthe isolation channel separating rail 22' is that it have sufficientwidth to isolate the cavity 28 from the channel 30, but not besufficiently wide to act as a rail itself.

FIG. 2d is a similar cross-section of an alternative relatively shallowisolation channel 30'. Because of the shallow depth, the air pressurealong the channel 30' increases above ambient fore to aft. Unlike thedeep channel 30 of FIG. 2c (which has near ambient pressure along itslength), in FIG. 2d the shallow channel air pressure will be a complexfunction of flying speed and skew angle an well as position (along itslength). Nevertheless, the shallow channel 30' provides a similarbenefit of reducing roll and loss of flying height over a range of skewangles.

Also, the isolation channel 30' and steps or chamfers may notnecessarily have constant width or depth along their length. It shouldbe noted also that the negative pressure cavity 28 need not be aconstant depth. The cavity depth may be stepped as at 29 of FIG. 1c(which is not prior art) or tapered in a variety of configurations toalter the negative pressure characteristics. These are variables thedesigner can manipulate for a specific application to provide customflying performance.

In FIG. 2d, rail 22 is 0.02" wide, channel 30' is 0.004" wide, andisolation channel separating rail 22' is 0.002" wide. The depth ofchannel 30' is approximately the same depth as negative pressure cavity28 (i.e., 350 microinches in the preferred embodiment). The chamfers 21and 23 are each approximately the same width as channel 30' (0.004"),and taper to a depth of about 40 microinches in the preferredembodiment.

FIGS. 3a-3k show alternative isolation channel embodiments. In FIG. 3a,both the width of the leading cavity 26 and the trailing portion of thenegative pressure cavity 28 are reduced, with corresponding expansionsof the leading taper and trailing rail widths. This configurationprovides for faster take-off, but the large trailing rails and smallertrailing negative cavity reduce pitch and reduce the increase in flyingheight at higher speeds.

In FIG. 3b, the isolation channels 30 and 32 are angled into andintersect the leading cavity 26. As skew increases, air flow into thechannel 30 or 32 more aligned with the direction of motion increases,while air flow into the other decreases. The net result is that more airis available to pressurize the trailing rail thus reducing roll.

In FIG. 3c, the leading cavity 26 is even further reduced and the crossrail 24 is made arrowhead shaped to enhance the funneling effect of airinto the downstream isolation channel. Moreover, the increased frontalarea provides greater lift, especially on take-off.

In FIG. 3d, the size of the cross rail is reduced from FIG. 3c so thatit is now "V" shaped and the isolation channels 30 and 32 are widened toconsume the entire leading cavity or recess. This design reducesover-pressure at the leading edge during high speed operation, increasesthe air flow into the downstream isolation channel and thus the skewcompensation and further increases the size of the negative pressurecavity 28 for lower flying height.

FIG. 3e is similar to FIG. 3b, however here the entire cross rail 24 isrecessed. Further, isolation channels 30 and 32 are shallower, andbroader than the isolation channels shown in FIG. 3b. Thus theircapacities are increased so that they provide an adequate source of airto pressurized rails 20 and 22. Furthermore, the rails include edgesteps (or tapers) 21 and 21' and 23 and 23' to ease pressurization atskew as discussed above. A key feature of this design is that thenegative pressure cavity 28 and isolation channels 30 and 32 areapproximately the same depth so that they may be formed during a singleion milling step. As well, cross rail recesses 24 and steps 21, 21', 23,and 23' are approximately the same depth so that they may be formedduring a single ion milling step.

In FIG. 3e, the overall length and width of the slider is 0.160"×0.121".The outside edge steps 21 and 21' are 0.004" wide. The inside steps 23and 23' are 0.002" wide. The isolation channels 30 and 32 are 0.006"wide. The isolation channel separating rails 20' and 22' are 0.002"wide. The negative pressure cavity 28 at its forward end is 0.066" wide,and at its trailing end is 0.589" wide. The leading edge taper 25, 27 is0.014" wide. The length and width of the leading cavity 26 is0.589"×0.031". The length of the cross rail 24 at its leading edge is0.040", and its length at its trailing edge is 0.070"; its width is0.013". The distance from the leading edge to the first channel bend is0.070", and to the second bend is 0.125". The depth of the steps 21,21', 23 and 23' and cross bar 24 recess is 40 μ".

FIG. 3f is a design similar to that of FIG. 3d with straight-angledisolation channels 30 and 32. The straight-angled channels are providedby removing the final outward bend therein. The longer angled insideedge of the downstream rail is more effective in pressurizing the airsupplied by the adjacent isolation channel 30 or 32, thus improving theroll compensation versus skew angle.

FIG. 3g is a design similar to that of 3f with the addition of a recessto cross rail 24, steps 23 and 23' along the trailing portions of rails22 and 20 respectively, and steps 21 and 21' in the outside edges of therails. The steps further improve the pressurization of the downstreamrail. The recess in the cross rail 24 reduces the chance of debriscollection at the cross rail 24 and further aids in breaking thenegative pressure cavity 28 vacuum at take-off.

FIGS. 3h-3j show alternative isolation channel arrangements designed toreduce the flying height sensitivity of the flyer to increased diskspeed.

In FIG. 3h, the isolation channels 30 and 32 do not extend the fulllength of the rails 20 and 22, but instead terminate and communicatewith the negative pressure cavity 28. An increase in flying height athigher speeds can be lessened by shortening the isolation channelseparating rails 20' and 22'. This allows greater interaction of thepositive and negative pressure effects.

In FIG. 3i, the isolation channel separating rails 20' and 22' arewidened at the trailing end of the negative pressure cavity 28 toprovide greater lift there.

In FIG. 3j, an island 52, is formed in a center region of the negativepressure cavity 28 adjacent the trailing edge of the cavity. The island52 is substantially the same height as the rails 20 and 22. A tapered orstepped forward end 54 increases pressurization of the island 52. Theisland 52 improves the flying characteristics of the slider by reducingfly height variation. Preferably, the slider has a near flat flyingprofile between an inner and an outer radius of the disk. In otherwords, the slider preferably flies at substantially the same heightabove the disk surface 11 (shown in FIG. 1c) at the inner radius as itflies at the outer radius. However, the velocity of the air beingdragged between the slider and the disk at the inner radius is less thanthe velocity at the outer radius. As a result, the positive pressurethat builds along the rails 20 and 22 is less at the inner radius thanat the outer radius causing the slider to fly lower at the inner radiusthan at the outer radius.

The island 52, however, reduces the effects on flying height caused bychanges in the air velocity. At low speeds, the air traveling beneaththe island 52 pressurizes the island and produces lift at the trailingedge of the slider. This lift increases the fly height at the innerradius of the disk. At high speeds, the effective pressure on the island52 is diminished, relative to the increasing effects of the negativepressure cavity 28. Therefore, the island 52 has almost no effect on flyheight at the outer radius of the disk. The overall result is a flatterflying profile between the inner radius and the outer radius of thedisk. The fly height variation is further reduced by positioning thetransducer on the island 52 since the island is generally coincidentwith a roll axis (not shown) of the slider.

FIG. 3k shows isolation channels 30 and 32 terminating generallyadjacent to side rail break points. The break points are where siderails 20 and 22 begin to broaden toward the trailing edge of the slider.The isolation channels 30 and 32 shown in FIG. 3k are shorter than thoseshown in FIG. 3h and allow for greater interaction of the positive andnegative pressure effects to further decrease flying

FIG. 3k also shows the edge steps 21 and 21'. However, unlike FIG. 3e,steps 21 and 21' do not extend the full length of the rails 20 and 22but terminate generally adjacent to the side rail break points. Theterminated edge steps 21 and 21' ease pressurization of the rails atskew and provide a large rail surface area near the trailing edge.Increasing the rail surface area near the trailing edge increasespressure on rails 20 and 22 during flight. The increased pressurestabilizes slider flight and provides a constant flying height throughvarying skew angles.

FIGS. 4a-4f illustrate selective spoiling of the negative pressure incavity 28 to both shorten take-off and compensate for skew effects.

FIG. 4a illustrates the basic spoiler concept. Here a circuitous,spoiler channel 31 is formed in cross rail 24 to communicate air betweenleading cavity or recess 26 and cavity 28. Spoiler channel 31 functionssimilarly to a recessed cross bar in reducing take-off speeds. The airflow through the spoiler channel 31 is proportional to the pressuredifference across the cross bar 24. The dimensions of the spoilerchannel 31 must be chosen so that there will not be a large reduction inthe negative pressure within the cavity 28 at higher flying speeds. Skewcompensation is provided by isolation channels 30 and 32.

Another variation of the negative pressure spoiler is shown in FIG. 4b.Here the spoiler channel 31 is slit into two angled segments. The effectof these angle channel segments increases when flying at positive ornegative skew angles. These spoiler channels 31 help reduce the overallloss of flying height when flying at skew angles. Isolation channels 30and 32 are angled into leading cavity 26 and perform in a similarfashion to those described for FIG. 3b.

FIG. 4c additionally provides a negative pressure cavity divider bar 36whose head 36' is arrow-shaped to provide two angled spoiler channels31' and 31" leading to negative pressure cavities 28' and 28"respectively. Spoilers 31' and 31" assist in breaking negative pressureon take-off, and the angles retard air entry into the cavities 28' and28" at speed. However, when the slider flies at a skew angle, one of thespoiler channels will begin to line up with the direction of motion andmore air will enter the corresponding downstream cavity, therebyreducing negative pressure effects in that cavity. Correspondingly, theother spoiler channel will become leas aligned with the direction ofmotion and less air will spoil the negative pressure in the upstream orleading cavity thereby increasing its negative pressure effects. Overallnegative pressure effect will be approximately the same, however, thetendency of the slider to roll with the leading rail high will belessened by the increased negative pressure in the leading cavity andthe reduced negative pressure in the trailing cavity.

FIG. 4d shows another variation on the same theme. Here the divider bar36 is slightly shortened and a leading triangular block 34 is added.Block 34 acts to reduce spoiling air flow into cavities 28' and 28" withno skew to a greater extent than the design of FIG. 4c. Spoiler channels31' and 31" are now crossed. Air flows through the crossed spoilerchannels 31' and 31" in a generally constricted manner as with the otherspoiler channels. However, when one of the channels becomes more alignedwith the direction of motion, the flow therethrough increases while flowsimultaneously decreases in the other channel. With better alignment,overall flow increases into the downstream negative pressure cavity, 28'or 28". With appropriate dimensions, the crossed spoiler channels 31'and 31" can be made to function as a fluidic-type device whereby thedifferences in the quantity of air flow to the divided cavities 28' and28" can be greatly enhanced providing a greater amount of slider rollcompensation.

FIG. 4e shows an alternative-spoiler design. Here a choke 31a isemployed which passes air at low speeds but which causes air flow toapproach a constant at higher flying speeds when the speed of the airwithin the choke 31a approaches sonic velocities. Thus, the primaryspoiling effect of air through the choke 31a occurs at low speed. Thisimproves the take-off characteristics at low speeds without spoiling thenegative pressure as much at higher speeds.

FIG. 4f shows an alternate spoiler channel location when isolationchannels 30 and 32 are included. The spoiler channels 31 may be locatedto communicate through the isolation channel separating rails 22' and20' between the negative pressure cavity 28 and the isolation channels30 and 32. Here the negative pressure cavity is divided into twocavities 28' and 28" and the isolation channels 30 and 32 are inclinedinto the leading cavity 26. At skew, the pressure in the downstreamisolation channel increases, thereby increasing the spoiling effect ofthe downstream cavity. Thus, roll is decreased by having relativelygreater negative pressure in the upstream cavity. This design has somesimilarities to the design in FIG. 4b. Here the spoiler channels 31' and31" are moved around to the sides and a divider bar 36 is added.

FIGS. 5a-5g illustrate several variations of a highly enlarged leadingedge taper section 25, 27 which increase lift to provide for shortertake-off. Each variation includes a pressure reduction channel 41anterior the cross rail to both reduce the over pressure of the leadingtaper at speed and also to maintain a high degree of negative pressurein cavity 28.

FIG. 5a illustrates the basic concept. A broad leading taper 25, 27 isprovided. Just aft of the leading taper and anterior a negative pressurecavity 28 pressure relief channel 41 is provided. Preferably, thischannel connects to ambient air pressure to vent air flowing past theleading taper 25, 27. In FIG. 5a, the vent is provided by channel 40leading to the forward edge of the slider.

The pressure relief channel anterior the negative pressure cavityprevents air scooped up by the leading taper from entering the negativepressure cavity 28 to spoil the negative pressure. This results in aslider that has both good take-off characteristics and low flyingheight. It has also been found to have a relatively constant flyingheight versus speed, a desirable property, and a higher flying height atlow speeds than a conventional NPAB slider.

FIG. 5b illustrates a variation which provides two lateral accesschannels 40' and 40" from the leading edge of the slider to the anteriorpressure relief channel 41. Additional edge steps or tapers 42' and 42"communicating between the leading sections of rails 20 and 22 and theaccess channel 40' and 40" act, in conjunction with access channels, toprovide air to the leading portion of the downstream or inside rail atskew. Cross rail 24 is shown recessed in this design. The effect issimilar to a limited isolation channel and may be particularly usefulfor sliders having only small skew angle variations.

FIG. 5c illustrates a variation which provides two lateral accesschannels 40' and 40" from the leading edge of the slider to the anteriorpressure relief channel 41. These access channels are in turn connectedto isolation channels 30 and 32. This design provides a high degree ofskew compensation with good take-off and flying height properties.

FIG. 5d illustrates a variation which provides two lateral accesschannels 40' and 40" communicating between the pressure relief channel41 and the side edges of the slider. These channels are in turnconnected to isolation channels 30 and 32. This design provides pressurereduction along the entire length of the leading taper 25, including infront of rails 20 and 22. As well, an optional spoiler channel 31connects from the anterior pressure relief channel to the negativepressure cavity 28 to assist in take-off as above described.

In this design, the frontal area of the leading taper 25 is maximizedfor fast take-off while the isolation channels provide skewcompensation. The presence of pressure relief channel 41 in front ofrails 20 and 22 reduces their effectiveness slightly so that high speedover-pressure from the large leading taper 25 is reduced.

FIG. 5e is another variation which connects the anterior pressure reliefchannel 41 to ambient air through isolation channels 30 and 32. Here theleading edge 25 frontal area is again maximized for fast take-off, skewcompensation is provided by the isolation channels 30 and 32.Pressurized air flowing past the front taper 25 enters the pressurerelief channel 41 and exits through isolation channels 30 and 32. Atskew, this air tends to preferably flow into the downstream isolationchannel, which enhances skew compensation. This design includes arecessed cross bar 24 which increases the air flow in the isolationchannels 30 and 32.

FIG. 5f is another variation which provides a single anterior pressurerelief channel 41 spanning the slider side edge-to-side edge. Airflowing past taper 25 exits through this channel 41. However, rail edgetapers or steps 44' and 44" connected to the channel 41 help pressurizethe rail from this source of air.

FIG. 5g illustrates another variation very similar to that of FIG. 3c.This configuration has the anterior pressure relief channel 41 of FIG.5a connected to isolation channels 30 and 32. However, the pressurerelief channel 41 is angled or V-shaped so that air will tend to f lowto the downstream isolation channel (30 or 32) enhancing skewcompensation.

At the trailing edge of the slider, the negative pressure cavity 28vents into channel 50, which communicates with the side edges of theslider. As well, isolation channels 32 and 30 have side vents 46'and46", respectively. The combination of side vents permits the transducerbearing portion 48 of the head to be a solid rail, which gives more areafor transducer elements and eliminates the need to machine-off a portionof the transducer materials during manufacture. This is important forcertain machining methods (e.g. laser machining) that cannot remove allof the transducer materials effectively.

The designer will appreciate that the described isolation channels 30and 32, anterior pressure relief channel 41, leading edge tapers 25, 27,spoiler channels 31, cavity dividers 36, and other particulars hereindescribed, may be selectively combined in other ways to produce a NPABslider having optimum properties for a given application.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A negative pressure air-bearing slider forsupporting a transducer proximate a rotating disc, comprising:a sliderbody having a surface with a leading edge, a trailing edge and first andsecond side edges; first and second raised side rails positioned alongthe first and second side edges, respectively; a raised cross railextending between the first and second raised side rails, the raisedcross rail having a leading edge and a trailing edge; a negativepressure cavity extending from the raised cross rail toward the trailingedge of the slider body and between the raised side rails; and a chokepositioned within the raised cross rail and widening from the leadingedge of the raised cross rail toward the trailing edge of the raisedcross rail, the choke defining a flow restriction which is dimensionedfor passing air through the flow restriction at low disc speeds inproportion to a pressure difference across the choke to spoil negativepressure in the negative pressure cavity as the slider takes-off fromthe disc and is dimensioned for passing air through the flow restrictionat a constant flow substantially independent of the pressure differenceduring acceleration of the disc to higher disc speeds to limit spoilingof negative pressure in the negative pressure cavity at the higher discspeeds.
 2. A system for storing and retrieving information, the systemcomprising:a rotating magnetic disc having a recording surface whichdrags air during disc rotation creating an air flow in parallel with atangential velocity of the disc rotation; a negative pressureair-bearing slider which is carried proximate to the recording surface,the slider comprising:a slider body having a surface facing therecording surface with a leading edge, a trailing edge and first andsecond side edges, wherein the airflow passes between the recordingsurface and the slider body surface; first and second raised side railspositioned along the first and second side edges, respectively; a raisedcross rail extending between the first and second raised side rails andhaving a leading edge and a trailing edge; a negative pressure cavityextending from the cross rail toward the trailing edge of the sliderbody and between the side rails; and a choke positioned within theraised cross rail and widening from the leading edge of the raised crossrail toward the trailing edge of the raised cross rail, wherein thechoke defines a restrictive air path which communicates between theleading edge of the raised cross rail and the negative pressure cavityand wherein the restrictive air path is dimensioned for passing the airflow through the restrictive air path in proportion to a pressuredifference across the choke as the slider takes-off from the recordingsurface at low disc speeds and is dimensioned for passing the air flowthrough the restrictive path at a constant flow substantiallyindependent of the pressure difference after the slider takes-off fromthe recording surface; and a transducer supported by the slider forcommunication with the recording surface.